#include <STC89C5xRC.H>


void Delayms(unsigned int xms)		//@11.0592MHz
{
	unsigned char i, j;
  while(xms)
	{
		i = 2;
		j = 199;
		do
		{
			while (--j);
		} while (--i);
		xms--;
	}
}
void main()
{
	//P2=0xfe;
	while(1)
	{
		if(P31 == 0)
		{
			P20 = 0;
			Delayms(500);
		}
		else
		{
			P20 = 1;
		}
	}
}